This invention pertains generally to fire control systems and particularly to systems of such type wherein the trajectory of a projectile in flight is controlled.
It has been proposed that so-called "beam riding" techniques be adapted to use with cannon-launched projectiles such as artillery shells. Thus, it has been proposed continuously to illuminate a projectile in flight with a coded beam of electromagnetic energy (the longitudinal centerline of such beam being controlled to follow the true ballistic trajectory of a projectile toward a selected target) and then to derive command signals within the projectile in flight in order to allow any deviation between the true and the actual ballistic trajectories to be corrected. Unfortunately, however, hitherto proposed beam riding techniques require that some means be provided in a cannon-launched projectile continuously to measure roll attitude when the projectile is in flight. While it is possible to use a roll gyroscope for such purpose (or to polarize the energy in the transmitted beam in some detectable manner), a penalty must be paid in terms of complexity and cost of the system.